Methods Compositions, Uses, and Kits Useful for Vitamin D Deficiency and Related Disorders

ABSTRACT

Methods for diagnosing, treating, and preventing catabolism-related vitamin D deficiency and related disorders; related compositions, apparatus and kits, are disclosed. A method involves measuring CYP24 expression and/or activity, or a proxy thereof such as FGF23 level, in a patient and correlating abnormally elevated CYP24 expression and/or activity with catabolism-related vitamin D deficiency or with susceptibility for catabolism-related vitamin D deficiency. In response to abnormally elevated CYP24 expression and/or activity, the method further includes administering a CYP24 inhibitor to the vitamin D deficient or at-risk patient, and preferably avoiding activation of the vitamin D binding receptor, such as by avoiding administration of active vitamin D compounds to such patients. Optionally, a vitamin D prohormone or prohormone can be administered.

CROSS-REFERENCE TO RELATED APPLICATIONS

The benefit under 35 U.S.C. §119(e) of U.S. Provisional PatentApplication Ser. Nos. 61/041,898 filed Apr. 2, 2008, and 61/161,292,filed Mar. 18, 2009, is hereby claimed, and the entire disclosuresthereof are hereby incorporated herein by reference.

BACKGROUND

1. Field of the Disclosure

The disclosure relates generally to methods for diagnosing and treatingdiseases and disorders, and related compositions and kits usefultherefor. More particularly, the disclosure relates to methods fordiagnosing and treating catabolism-related vitamin D deficiency andsusceptibility thereto, related compositions and kits, and methods forpreventing and treating related disorders.

2. Brief Description of Related Technology

Humans acquire vitamin D from dietary sources and from the UVlight-dependent conversion of 7-dehydroxcholesterol to vitamin D₃.Vitamin D₃ (or cholecalciferol) and vitamin D₂ (or ergocalciferol) arecollectively referred to as “vitamin D” and are fat-soluble precursorsto the active vitamin D hormones. Metabolism of vitamin D₃ and vitaminD₂ occurs primarily in the liver to produce 25-hydroxyvitamin D₃ and25-hydroxyvitamin D₂, respectively (collectively referred to herein as“25-hydroxyvitamin D”), which are prohormones of the respective activevitamin D hormones. Further metabolic activation of these vitamin Dprohormones occurs mainly in the kidneys by a cytochrome P450 enzyme,CYP27B. CYP27B is also expressed in many extra-renal vitamin D targettissues and can effect local activation of 25-hydroxyvitamin D toproduce autocrine and/or paracrine hormonal responses. Specifically,25-hydroxyvitamin D₃ is metabolized to the active hormone1,25-dihydroxyvitamin D₃ (or calcitriol) and 25-hydroxyvitamin D₂ ismetabolized to the active hormone 1,25-dihydroxyvitamin D₂ (collectivelyreferred to herein as “1,25-dihydroxyvitamin D”).

The vitamin D hormones regulate a variety of cellular processes viainteractions with vitamin D receptors (VDR). In particular, the vitaminD hormones regulate blood calcium levels by controlling the absorptionof dietary calcium by the small intestine and the reabsorption ofcalcium by the kidneys. Excessive hormone levels can lead to abnormallyelevated urine calcium (hypercalciuria), blood calcium (hypercalcemia)and blood phosphorus (hyperphosphatemia). Vitamin D deficiency, on theother hand, is associated with secondary hyperparathyroidism,parathyroid gland hyperplasia, hypocalcemia, chronic kidney disease(CKD), and metabolic bone diseases such as osteitis fibrosa cystica,osteomalacia, rickets, osteoporosis, and extraskeletal calcification.Vitamin D hormone has been reported to have many diverse “non-classical”biologic effects beyond its “classical” effects on the parathyroidhormone system. Such effects have been reported in connection withcellular proliferation, the immune system and the cardiovascular system,including the renin-angiotensin system, blood pressure, cellular growthand differentiation, antifibrosis, red blood cell formation, hairgrowth, and muscular function.

Catabolism of vitamin D prohormones, hormones, and analogs isaccomplished through the action of cytochrome P450 enzymes. Thecytochrome P450 enzyme CYP24 catalyzes the first step in the catabolismof various vitamin D compounds. In particular, for example, CYP24carries out the conversion of 25-hydroxyvitamin D₃ to24,25-dihydroxyvitamin D₃ and the conversion of 1,25-dihydroxyvitamin D₃(calcitriol) to 1,24,25-trihydroxyvitamin D₃ eventually giving rise tocalcitroic acid. CYP24 can also hydroxylate at the 23 position,resulting in the production of the terminal metabolite1,25-dihydroxyvitamin D₃-26,23-lactone. Further processing by Phase IIcatabolic enzymes ultimately leads to clearance of vitamin D compoundsfrom the body.

SUMMARY

One aspect of the disclosure herein is a method of diagnosingsusceptibility for catabolism-related vitamin D deficiency in a patient,including measuring a patient's level of CYP24 expression and/oractivity, or a proxy indicative thereof, for example by obtaining atissue, blood, or cell sample from a patient and assaying the sample forCYP24 expression and/or activity, or a proxy indicative thereof, whereinabnormally elevated CYP24 expression and/or activity indicates asusceptibility for catabolism-related vitamin D deficiency. In oneembodiment, the patient is vitamin D replete, and the method furtherincludes inhibiting and/or preventing vitamin D deficiency byadministering a CYP24 inhibitor to the patient in response to abnormallyelevated CYP24 expression and/or activity. In another embodiment, thepatient is vitamin D deficient, and the method further includes treatingthe vitamin D deficiency by administering a CYP24 inhibitor to thepatient in response to abnormally elevated CYP24 expression and/oractivity.

Another aspect of the disclosure herein is a method of diagnosingsusceptibility for catabolism-related vitamin D deficiency in a patient,including measuring a patient's level of FGF23, for example by obtaininga tissue, blood, or cell sample from a patient and assaying the samplefor FGF23 concentration, wherein abnormally elevated FGF23 concentrationindicates a susceptibility for catabolism-related vitamin D deficiency.The method can further include any one of the treatment or preventionmethods described herein.

Another aspect of the disclosure herein is a method of diagnosing andtreating a patient, including measuring a patient's CYP24 expressionand/or activity, or a proxy indicative thereof, and administering aCYP24 inhibitor to the patient in response to abnormally elevated CYP24expression and/or activity. The method can further include obtaining atissue, blood, or cell sample from the patient and assaying the samplefor CYP24 expression and/or activity, or a proxy indicative thereof.

Preferably at the time of the measurement of CYP24 expression and/oractivity, or proxy indicative thereof, the patient is not undergoingactive vitamin D therapy.

Preferably, the patient is one who does not have cancer.

The method can further include measuring the patient's 25-hydroxyvitaminD levels and treating vitamin D deficiency by administering the CYP24inhibitor to a vitamin D deficient patient.

The method can further include administering to the patient one or moreof vitamin D prehormones, prohormones, and analogs of any of theforegoing, preferably a compound selected from cholecalciferol,ergocalciferol, 25-hydroxyvitamin D2, 25-hydroxyvitamin D3, andcombinations thereof. For example the therapy can include administrationof 25-hydroxyvitamin D3. Preferably the therapy includes administrationof a therapeutically effective amount of 25-hydroxyvitamin D3 to restorethe patient's 25-hydroxyvitamin D levels to at least 30 ng/mL.

The method can further include measuring the patient's 25-hydroxyvitaminD levels and inhibiting and/or preventing vitamin D deficiency byadministering the CYP24 inhibitor to a vitamin D replete patient.

In one type of embodiment, the patient has Chronic Kidney Disease, forexample selected from Stage 1 and Stage 2, or selected from Stage 3 andStage 4.

In one type of embodiment, the patient has hyperparathyroidism. Forexample, the patient's PTH level is above the target range for thepatient's Stage of CKD.

In one type of embodiment, the patient has a deficiency in1,25-dihydroxyvitamin D3.

The method can further include avoiding active vitamin D therapy orreducing the level of or omitting active vitamin D therapy if thepatient is undergoing active vitamin D therapy.

The method can further include administering 25-hydroxyvitamin D to thepatient in an amount sufficient to increase 1,25-dihydroxyvitamin Dlevels.

In one embodiment, the CYP24 inhibitor is also a vitamin D receptoragonist.

The method can include measuring the level of FGF23 in the patient as aproxy for the level of CYP24 expression and/or activity, wherein a levelof FGF23 greater than the upper value of the normal range indicatesabnormally elevated CYP24 expression. For example, a level of FGF23 atleast two times, at least four times, at least 10 times, or at least 40times greater than the upper value of the normal range indicatesabnormally elevated CYP24 expression.

The method can include measuring the concentration of one or morecatabolic byproducts of CYP24 in serum or another bodily fluid as aproxy for CYP24 activity.

The method can further include measuring the concentration of one ormore precursors to the one or more catabolic byproducts of CYP24 inserum or another bodily fluid and calculating a ratio of concentrationsof one or more catabolic byproducts of CYP24 to serum concentrations ofone or more corresponding precursors as a proxy for CYP24 activity.

In one embodiment, the catabolic byproducts of CYP24 include one or bothof 24,25-dihydroxyvitamin D and 1,24,25-trihydroxyvitamin D.

In one embodiment, the measuring of CYP24 activity includes measuringone or more ratios selected from the group consisting of24,25-dihydroxyvitamin D to 25-hydroxyvitamin D and1,24,25-trihydroxyvitamin D to 1,25-dihydroxyvitamin D.

In one embodiment, the catabolic byproducts of CYP24 include the24-hydroxylated and/or 23-hydroxylated catabolic byproducts of one ormore members selected from the group consisting of paricalcitol,doxercalciferol, 22-oxacalcitriol, dihydrotachysterol, and26,26,26,27,27,27-hexafluorocoalcitriol (falecalcitriol).

In one embodiment, the measuring of CYP24 expression and/or activity, orproxy indicative thereof follows acute or chronic administration of aCYP24 substrate. In this embodiment, preferably the CYP24 substrate isnot a dual-action inhibitor and VDR agonist, as described below.

In one embodiment, one or more measurements comprise serumconcentrations.

In one embodiment, the measuring of CYP24 expression includes measuringCYP24 mRNA in tissues, plasma, or cells.

In one embodiment, the measuring of CYP24 expression includes measuringCYP24 protein in tissues, plasma, or cells.

In one embodiment, the measuring of CYP24 activity includes measuringCYP24 enzymatic activity in tissues, plasma, or cells.

In one embodiment, the tissues or cells are selected from the groupconsisting of kidney tissue, liver tissue, parathyroid gland tissue,peripheral blood mononuclear cells, and buccal cells.

In one embodiment, the abnormally elevated CYP24 expression and/oractivity is at least 2-fold, at least 3-fold, at least 4-fold, at least10-fold, or at least 100-fold increased over normal CYP24 expressionand/or activity.

Another aspect of the disclosure includes a kit, including an assay formeasuring the levels of one or more CYP24 catabolic byproducts, andinstructions for practicing a method described herein. The kit canfurther include an assay for measuring the levels of one or morecorresponding precursors.

Another aspect of the disclosure includes a kit including an assay formeasuring the level of CYP24 protein, and instructions for practicing amethod described herein. The assay can include an immobilized anti-CYP24antibody, and a labeled anti-CYP24 antibody.

Another aspect of the disclosure includes a pharmaceutical formulationfor treating or preventing vitamin D deficiency including an effectiveamount of a CYP24 inhibitor. The formulation can further include aneffective amount of 25-hydroxyvitamin D3.

Another aspect of the disclosure includes a pharmaceutical formulationfor treating or preventing hyperparathyroidism including an effectiveamount of a CYP24 inhibitor. The formulation can further include aneffective amount of 25-hydroxyvitamin D3. The pharmaceutical formulationcan be for treating hyperparathyroidism secondary to Chronic KidneyDisease, for example Stage 3 or Stage 4 CKD.

Another aspect of the disclosure includes a CYP24 inhibitor for use intreating or preventing vitamin D deficiency.

Another aspect of the disclosure includes a CYP24 inhibitor for use intreating or preventing hyperparathyroidism, for examplehyperparathyroidism secondary to Chronic Kidney Disease, for exampleStage 3 or Stage 4 CKD.

Another aspect of the disclosure includes use of a CYP24 inhibitor forthe manufacture of a medicament for treating or preventing vitamin Ddeficiency.

Another aspect of the disclosure includes use of a CYP24 inhibitor forthe manufacture of a medicament for treating or preventinghyperparathyroidism, for example hyperparathyroidism secondary toChronic Kidney Disease, for example Stage 3 or Stage 4 CKD.

For the compositions, methods, uses, and kits described herein,preferred features, such as components, compositional ranges thereof,substituents, conditions (e.g., characteristics of patient populations),and method steps, can be selected from the various examples providedherein.

Further aspects and advantages will be apparent to those of ordinaryskill in the art from a review of the following detailed description,taken in conjunction with the drawings. While the method is susceptibleof embodiments in various forms, the description hereafter includesspecific embodiments with the understanding that the disclosure isillustrative, and is not intended to limit the invention to the specificembodiments described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

For further facilitating the understanding of the present invention,nine drawing figures are appended hereto.

FIG. 1 shows a graph of serum parathyroid hormone (PTH) levels over timein rats fed an adenine-rich diet or a control diet.

FIG. 2 shows a graph of serum parathyroid hormone (PTH) levels inadenine-fed rats treated with three different vitamin D compounds forone week.

FIG. 3 shows a graph of 1,25-(OH)₂-D₃ (calcitriol) levels in adenine-fedand control-diet-fed rats and in adenine-fed animals treated with threedifferent vitamin D compounds.

FIG. 4 shows a graph of CYP24 expression in kidney tissue fromadenine-fed and control-diet fed rats and from adenine-fed animalstreated with three different vitamin D compounds. RFI indicates therelative fold induction.

FIG. 5 shows a graph of CYP24 expression in parathyroid gland tissuefrom adenine-fed and control-diet fed rats and from adenine-fed animalstreated with three different vitamin D compounds.

FIG. 6 shows a graph of serum FGF23 levels in adenine-fed andcontrol-diet fed rats and in adenine-fed animals treated with threedifferent vitamin D compounds.

FIG. 7 shows a graph of FGF23 levels and osteoclacin levels in kidneytissue from adenine-fed and control-diet fed rats.

FIG. 8 shows a graph of relative CYP24 induction in rats treated withvitamin D (25-hydroxyvitamin D₂ and 25-hydroxyvitamin D₃) for 2 weeks.

FIG. 9 shows changes 25-OH-D levels in humans in response toadministration of placebo and(5Z,7E,16Z,23E)-(1S,3R)-25-nor-25-t-butylsulfonyl-9,10-seco-5,7,10(19),16,23-cholestapentaene-1,3-diol.

FIG. 10 shows relative CYP24 induction in kidney tissue in normal andadenine-induced uremic rats, showing that basal expression of CYP24(vehicle) and induced expression of CYP24 by 1,25-dihydroxyvitamin D₃(1α,25(OH)₂D₃).

FIG. 11 shows relative CYP24 induction in parathyroid gland tissue innormal and adenine-induced uremic rats, showing that basal expression ofCYP24 (vehicle) and induced expression of CYP24 by 1,25-dihydroxyvitaminD₃ (1α,25(OH)₂D₃).

FIG. 12 shows relative expression of CYP24 and CYP27B1 in normal rats,adenine-induced uremic rats, and adenine-induced uremic rats treatedwith 1,25-dihydroxyvitamin D₃, with resultant exacerbation of vitamin Ddeficiency.

FIG. 13 shows relative expression of CYP24 and CYP27B1 in normal ratsversus normal rats on a vitamin-D deficient diet, and betweenadenine-induced uremic rats on a normal diet and on a vitamin-Ddeficient diet.

FIG. 14 shows relative induction of CYP24 expression in HEK cellsincubated with 1,25-dihydroxyvitamin D₃ alone or with a CYP24 inhibitor.

FIG. 15 shows the 3H-thymidine incorporation (%) in HEK cells treatedwith 1,25-dihydroxyvitamin D₃ alone or in combination with a CYP24inhibitor at various concentrations.

FIG. 16 shows the relative expression of CYP24 in HPK1a-ras cellstreated with 1,25-dihydroxyvitamin D₃ alone or in combination withFGF23.

FIG. 17 shows the relative induction of CYP24 in normal rats versusnormal rats fed a vitamin D deficient diet, and normal rats fed avitamin D deficient diet that were treated with various concentrationsof 25-hydroxyvitamin D₃.

FIG. 18 shows the relative induction of CYP24 in rats fed a normal dietsupplemented with adenine (“Adenine Vehicle”) versus a vitamin Ddeficient diet supplemented with adenine and versus rats fed a vitamin Ddeficient diet supplemented with adenine and treated with variousconcentrations of 25-hydroxyvitamin D₃.

FIG. 19 shows the effect of 25-hydroxyvitamin D₃ on the concentration of1,25-dihydroxyvitamin D₃ in uremic vitamin D deficient rats versusotherwise normal vitamin D deficient rats.

DETAILED DESCRIPTION

“Vitamin D deficiency” is generally defined as a condition in a humanpatient or other mammal in which serum 25-hydroxyvitamin D levels isbelow 30 ng/mL (see National Kidney Foundation guidelines, NKF, Am. J.Kidney Dis. 42:S1-S202 (2003), incorporated herein by reference).“Vitamin D deficiency” includes “vitamin D insufficiency,” defined asserum 25-hydroxyvitamin D of at least 16 ng/mL and less than 30 ng/mL,“mild” vitamin D deficiency, defined as serum 25-hydroxyvitamin D of5-15 ng/mL, and “severe” vitamin D deficiency, defined as serum25-hydroxyvitamin D below 5 ng/mL.

As used herein, the term “vitamin D replete” is defined as a conditionin a human patient or other mammal in which serum 25-hydroxyvitamin Dlevels is at or above 30 ng/mL.

The term “at risk” as used herein generally refers to those patientpopulations having characteristics or diseases associated with vitamin Ddeficiency. Specific examples include, but are not limited to, subjectswith Stage 1, 2, 3, 4 or 5 chronic kidney disease; infants, children andadults that do not drink vitamin D fortified milk (e g lactoseintolerant subjects, subjects with milk allergy, vegetarians who do notconsume milk, and breast fed infants); subjects with rickets; subjectswith dark skin (e.g., in the U.S., 42% of African American women between15 and 49 years of age were vitamin D deficient compared to 4% of whitewomen); the elderly (who have a reduced ability to synthesize vitamin Dand also are more likely to stay indoors); chronically or acutely andseverely ill adults (who are likely to stay indoors, in hospitals, inintensive care facilities, institutional and assisted-care facilitiesincluding subjects with Alzheimer's disease or mentally ill); subjectswho cover all exposed skin (such as members of certain religions orcultures); subjects who always use sunscreen (e.g., the application ofsunscreen with a Sun Protection Factor (SPF) value of 8 reducesproduction of vitamin D by 95%, and higher SPF values may further reducevitamin D); subjects with fat malabsorption syndromes (including but notlimited to cystic fibrosis, cholestatic liver disease, other liverdisease, gallbladder disease, pancreatic enzyme deficiency, Crohn'sdisease, inflammatory bowel disease, sprue or celiac disease, orsurgical removal of part or all of the stomach and/or intestines);subjects with inflammatory bowel disease; subjects with Crohn's disease;subjects who have had small bowel resections; subjects with gum disease;subjects taking medications that increase the catabolism of vitamin D,including phenytoin, fosphenytoin, phenobarbital, carbamazepine, andrifampin; subjects taking medications that reduce absorption of vitaminD, including cholestyramine, colestipol, orlistat, mineral oil, and fatsubstitutes; subjects taking medications that inhibit activation ofvitamin D, including ketoconazole; subjects taking medications thatdecrease calcium absorption, including corticosteroids; subjects withobesity, diabetes mellitus, insulin resistance syndrome, endothelialdysfunction (vitamin D deposited in body fat stores is lessbioavailable); subjects with osteoporosis; postmenopausal women;individuals with cardiovascular disease, atherosclerosis, and/or heartfailure; and/or critically-ill hospitalized subjects.

In one embodiment, the patient does not have cancer. A “cancer” refersto the presence of cells possessing characteristics typical ofcancer-causing cells, such as uncontrolled proliferation, immortality,metastatic potential, rapid growth and proliferation rate, and certaincharacteristic morphological features. Often, cancer cells will be inthe form of a tumor, but such cells may exist alone within a human oranimal, or may be a non-tumorigenic cancer cell, such as a leukemiacell. Cancers include, but are not limited to breast cancer, lungcancer, bronchus cancer, colorectal cancer, prostate cancer, pancreascancer, stomach cancer, ovarian cancer, urinary bladder cancer, brain orcentral nervous system cancer, peripheral nervous system cancer,esophageal cancer, cervical cancer, a melanoma, uterine or endometrialcancer, cancer of the oral cavity or pharynx, liver cancer, kidneycancer, testis cancer, biliary tract cancer, small bowel or appendixcancer, salivary gland cancer, thyroid gland cancer, adrenal glandcancer, osteosarcoma, and a chondrosarcoma.

As used herein, the term “hyperparathyroidism” refers to one or more ofprimary hyperparathyroidism, secondary hyperparathyroidism,hyperparathyroidism secondary to chronic kidney disease (Stage 3, 4 or5) and hyperparathyroidism secondary to vitamin D deficiency.

The terms “subject” and “patient” as used herein generally includehumans, mammals (e.g., dogs, cats, rodents, sheep, horses, cows, goats),veterinary animals and zoo animals, preferably humans.

The term “CYP24 expression and/or activity” as used herein generallyincludes transcription to produce CYP24 mRNA, translation to produceCYP24 protein, and the combination of transcription and translation toproduce CYP24 protein, as well as activity of the CYP24 enzyme directlyor by calculating the ratio of CYP24 products to CYP24 substrates.

As used herein, the term “vitamin D compound” generally includes vitaminD pre-hormones (e.g., cholecalciferol and ergocalciferol), vitamin Dprohormones (e.g., 1α-hydroxyvitamin D₃, 1α-hydroxyvitamin D₃,25-hydroxyvitamin D₃, and 25-hydroxyvitamin D₂), active vitamin Dhormones, analogs of the foregoing, and combinations of any of theforegoing. Specific examples include, but are not limited to, vitamin D₃(cholecalciferol), vitamin D₂ (ergocalciferol), 25-hydroxyvitamin D₃,25-hydroxyvitamin D7, 1α,25-dihydroxyvitamin D₃, 1α,25-dihydroxyvitaminD₂, 1α,25-dihydroxyvitamin D₄, and vitamin D analogs (including allhydroxy and dihydroxy forms), including 1,25-dihydroxy-19-nor-vitaminD₂, 22-oxacalcitriol, dihydrotachysterol, and26,26,26,27,27,27-hexafluorocalcitriol (falecalcitriol).

As used herein, the terms “active vitamin D” and “activated vitamin D”refer to a vitamin D compound that is hydroxylated in at least the 1αposition. Active vitamin D compounds include calcitriol,1,25-dihydroxyvitamin D₂, alfacalcidol, doxercalciferol,22-oxacalcitriol, and paricalcitol.

As used herein, the phrase “therapeutically effective amount” refers toan amount of therapeutic or prophylactic agent (e.g., a CYP24 inhibitoror dual action CYP24 inhibitor and VDR agonist) that would beappropriate for an embodiment of the present invention, and that willelicit the desired therapeutic or prophylactic effect or response whenadministered in accordance with the desired treatment regimen. Morespecifically, a “therapeutically effective amount” means an amounteffective to prevent development of, to eliminate, to correct, or toretard the progression of the relevant condition, e.g. vitamin Ddeficiency. Determination of a therapeutically effective amount is wellwithin the capability of those skilled in the art, especially in lightof the detailed disclosure provided herein.

A “therapeutically effective dose” refers to that amount of the activeingredients that results in achieving the desired effect. Toxicity andtherapeutic efficacy of such active ingredients can be determined bystandard pharmaceutical procedures in cell cultures or experimentalanimals, e.g., determining the LD₅₀ (the dose lethal to 50% of thepopulation) and the ED₅₀ (the dose therapeutically effective in 50% ofthe population). The dose ratio between toxic and therapeutic effects isthe therapeutic index, which is expressed as the ratio between LD₅₀ andED₅₀. A high therapeutic index is preferred. The data obtained can beused in formulating a range of dosage for use in humans. The dosage ofthe active ingredients preferably lies within a range of circulatingconcentrations that include the ED₅₀ with little or no toxicity. Thedosage can vary within this range depending upon the dosage formemployed, and the route of administration utilized.

As used herein, the term “comprising” indicates the potential inclusionof other agents, elements, steps, or features, in addition to thosespecified.

One aspect of the disclosure provides a method for diagnosingcatabolism-related vitamin D deficiency. The method includes measuringCYP24 expression and/or activity in a vitamin D deficient patient andcorrelating abnormally elevated CYP24 expression and/or activity withcatabolism-related vitamin D deficiency. In response to abnormallyelevated CYP24 expression and/or activity, the method can furtherinclude administering a CYP24 inhibitor to the vitamin D deficientpatient.

Another aspect of the disclosure provides a method for diagnosingsusceptibility for catabolism-related vitamin D deficiency. The methodincludes measuring CYP24 expression and/or activity in a patient andcorrelating abnormally elevated CYP24 expression and/or activity withsusceptibility for catabolism-related vitamin D deficiency. In responseto abnormally elevated CYP24 expression and/or activity in a vitamin Dreplete patient, the method can further include inhibiting and/orpreventing vitamin D deficiency by administering a CYP24 inhibitor tothe vitamin D replete patient. In response to abnormally elevated CYP24expression and/or activity in a vitamin D deficient patient, the methodcan further include treating vitamin D deficiency by administering aCYP24 inhibitor to the vitamin D deficient patient.

Yet another aspect of the disclosure provides a method for treating orpreventing vitamin D deficiency and/or hyperparathyroidism. The methodincludes measuring CYP24 expression and/or activity in a patient, or aproxy therefor, and administering a CYP24 inhibitor to the patient inresponse to abnormally elevated CYP24 expression and/or activity. Themethod can include treating vitamin D deficiency by administering theCYP24 inhibitor to a vitamin D deficient patient having abnormallyelevated CYP24 expression and/or activity. The method can furtherinclude inhibiting and/or preventing vitamin D deficiency byadministering the CYP24 inhibitor to a vitamin D replete patient havingabnormally elevated CYP24 expression and/or activity. The method caninclude inhibiting and/or preventing hyperparathyroidism byadministering the CYP24 inhibitor to a patient having abnormallyelevated CYP24 expression and/or activity. The method can also includeinhibiting and/or preventing a deficiency of 1,25-dihydroxyvitamin D byadministering the CYP24 inhibitor to a patient having abnormallyelevated CYP24 expression and/or activity.

Another aspect of the disclosure provides a method for treating orpreventing vitamin D deficiency in a patient. The method includesmeasuring CYP24 expression and/or activity in the patient andadministering a CYP24 inhibitor to the patient in response to abnormallyelevated CYP24 expression and/or activity. The method further includesavoiding exacerbation of increased CYP24 levels and vitamin D deficiencyin the patient in response to abnormally elevated CYP24 expressionand/or activity, e.g. by reducing, avoiding (omitting), or ceasingactivation of the vitamin D binding receptor (VDR) by outsideinfluences, for example by reducing, avoiding (omitting), or ceasingadministration of active vitamin D compounds. The method can furtherinclude administering a vitamin D supplement to the patient, such as byadministering 25-hydroxyvitamin D (e.g., 25-hydroxyvitamin D₃) to thepatient. The method can further include measuring the intact parathyroidhormone (PTH) levels and 25-hydroxyvitamin D levels in the patient. Inone embodiment, the patient has abnormally elevated PTH level and normal25-hydroxyvitamin D level. In another embodiment, the patient hasabnormally elevated PTH levels and abnormally decreased25-hydroxyvitamin D level (e.g., vitamin D deficiency). In anotherembodiment, the patient has normal PTH levels and abnormally decreased25-hydroxyvitamin D levels, The method can further include measuringglomerular filtration rate (GFR) in the patient to determine the Stageof Chronic Kidney Disease. In one embodiment, the patient will have CKDselected from stages 1-5. In another embodiment, the patient will haveCKD selected from stages 1 and 2. In another embodiment, the patientwill have CKD selected from stages 3 and 4.

One embodiment of the disclosure provides for measuring CYP24 activityby measuring the level of fibroblast growth factor-23 (FGF23) in apatient. Another embodiment provides for measuring CYP24 expressionand/or activity by measuring the level of one or more catabolicbyproducts of CYP24 (including but not limited to,24,25-dihydroxyvitamin D₃, 25-hydroxyvitamin D₃-26,23-lactone,1,24,25-trihydroxyvitamin D₃, 24,25-dihydroxyvitamin D₂, or1,24,25-trihydroxyvitamin D₂ or the terminal products of CYP24 activityon vitamin D3 metabolites including calcitroic acid or1,25-(OH)₂D₃-26,23-lactone). Another embodiment provides for measuringCYP24 activity by measuring ratios of one or more catabolic byproductsof CYP24 to one or more corresponding precursors (e.g. the ratio of24,25-dihydroxyvitamin D to 25-hydroxyvitamin D, or the ratio of1,24,25-trihydroxyvitamin D to 1,25-dihydroxyvitamin D). Still otherembodiments provide for measuring CYP24 expression by measuring thelevel of CYP24 mRNA in a patient, the level of CYP24 protein in apatient, and/or the level of CYP24 enzyme activity in a patient. Anotherembodiment provides for measuring CYP24 activity by measuring CYP24metabolite(s) of other CYP24 substrates which could be introduced (e.g.,by injection), metabolized by CYP24, and then measured.

Another aspect of the disclosure provides a kit for diagnosingcatabolism-related vitamin D deficiency. In one embodiment, the kitincludes an assay or other apparatus for measuring CYP24 mRNA, proteinor enzymatic activity, and instructions for use, for example accordingto a method disclosed herein.

The diagnostic kit and methods disclosed herein are contemplated toinclude embodiments including any combination of one or more of theadditional optional elements, features, and steps further describedbelow (including those shown in the figures), unless stated otherwise.

It also is specifically understood that any numerical value recitedherein includes all values from the lower value to the upper value,i.e., all possible combinations of numerical values between the lowestvalue and the highest value enumerated are to be considered to beexpressly stated in this application. For example, if a concentrationrange or a beneficial effect range is stated as 1% to 50%, it isintended that values such as 2% to 40%, 10% to 30%, or 1% to 3%, etc.,are expressly enumerated in this specification. These are only examplesof what is specifically intended.

In one aspect, the present disclosure provides a method of diagnosingcatabolism-related vitamin D deficiency. The method includes measuringCYP24 expression and/or activity in a vitamin D deficient patient andcorrelating abnormally elevated CYP24 expression and/or activity withcatabolism-related vitamin D deficiency. In response to abnormallyelevated CYP24 expression and/or activity, the method can furtherinclude administering a CYP24 inhibitor to the vitamin D deficientpatient.

In another aspect, the present disclosure provides a method ofdiagnosing susceptibility for catabolism-related vitamin D deficiency.The method includes measuring CYP24 expression and/or activity in apatient and correlating abnormally elevated CYP24 expression and/oractivity with susceptibility for catabolism-related vitamin Ddeficiency. In response to abnormally elevated CYP24 expression and/oractivity in a vitamin D replete patient, the method can further includeinhibiting and/or preventing vitamin D deficiency by administering aCYP24 inhibitor to the vitamin D replete patient. In response toabnormally elevated CYP24 expression and/or activity in a vitamin Ddeficient patient, the method can further include treating vitamin Ddeficiency by administering a CYP24 inhibitor to the vitamin D deficientpatient.

In yet another aspect, the present disclosure provides a method oftreating or preventing vitamin D deficiency and/or hyperparathyroidism.The method includes measuring CYP24 expression and/or activity, or aproxy therefor, in a patient and administering a CYP24 inhibitor to thepatient in response to abnormally elevated CYP24 expression and/oractivity. The method can include treating vitamin D deficiency byadministering the CYP24 inhibitor to a vitamin D deficient patienthaving abnormally elevated CYP24 expression and/or activity. The methodcan include inhibiting and/or preventing vitamin D deficiency byadministering the CYP24 inhibitor to a vitamin D replete patient havingabnormally elevated CYP24 expression and/or activity. The method caninclude inhibiting and/or preventing hyperparathyroidism byadministering the CYP24 inhibitor to a patient having abnormallyelevated CYP24 expression and/or activity. The method can also includeinhibiting and/or preventing a deficiency of 1,25-dihydroxyvitamin D byadministering the CYP24 inhibitor to a patient having abnormallyelevated CYP24 expression and/or activity.

Vitamin D deficiency is associated with a host of additional diseasesand disorders, including secondary hyperparathyroidism, parathyroidgland hyperplasia, hypocalcemia, psoriasis, chronic kidney disease(CKD), and metabolic bone diseases such as fibrogenesis imperfectaossium, osteitis fibrosa cystica, osteomalacia, rickets, osteoporosis,osteopenia, osteosclerosis, renal osteodystrophy, and extraskeletalcalcification. The methods in accordance with the present disclosurealso are useful for treating or preventing diseases or disordersassociated with vitamin D deficiency.

The current standard of care for CKD patients states that patientsshould have their PTH and 25-hydroxyvitamin D levels measured. In Stage3 and Stage 4 patients, if the plasma intact parathyroid (PTH) level iselevated (e.g., above the target range for the stage of CKD) and the25-hydroxyvitamin D is decreased (<30 ng/ml), then the patient istreated with a vitamin D₂ supplement (ergocalciferol). See “Guideline 7:Prevention And Treatment Of Vitamin D Insufficiency And Vitamin DDeficiency In People With CKD (Algorithm 1)” of National KidneyFoundation K/DOQI clinical practice guidelines for bone metabolism anddisease in chronic kidney disease, Am J Kidney Dis 42:S1-S202, 2003(Suppl 3), incorporated herein by reference. For CKD Stage 3 (GFR Range30-59 ml/min/1.73 m²), the target PTH level is 35-70 pg/ml (3.85-7.7pmol/L). For CKD Stage 4 (GFR Range 15-29 ml/min/1.73 m²), the targetPTH level is 70-110 pg/ml (7.7-12.1 pmol/L).

On the other hand, if the PTH level is above the target range for thestage of CKD and the serum levels of 25-hydroxyvitamin D are >30 ng/ml,then the patient is treated with an active vitamin D hormone (e.g.,calcitriol, alfacalcidol, or doxercalciferol). See “Guideline 8A: ActiveVitamin D Therapy In Stages 3 And 4 CKD (Algorithm 2)” of NationalKidney Foundation K/DOQI clinical practice guidelines for bonemetabolism and disease in chronic kidney disease, Am J Kidney Dis42:S1-S202, 2003 (Suppl 3), incorporated herein by reference.

Without intending to be bound by any particular theory, FIG. 12 showsthat if the level of 25-hydroxyvitamin D is normal, treating with anactive vitamin D hormone per guidelines will increase the levels ofCYP24, and therefore will exacerbate vitamin D deficiency despitereducing PTH levels. In patients with chronic kidney disease andelevated PTH levels, CYP24 overactivity should be managed by (a) using aCYP24 inhibitor and/or (b) avoiding further exacerbation of increasedCYP24 levels and vitamin D deficiency.

Accordingly, another aspect of the disclosure provides a method fortreating or preventing hyperparathyroidism secondary to chronic kidneydisease (preferably Stages 3 and 4) in a patient. The method includesmeasuring CYP24 expression and/or activity in the patient andadministering a CYP24 inhibitor to the patient in response to abnormallyelevated CYP24 expression and/or activity. The method preferably furtherincludes avoiding exacerbation of increased CYP24 levels and vitamin Ddeficiency, if present, by avoiding administration of active vitamin D.The method can further include administering vitamin D supplementationto the patient, preferably with 25-hydroxyvitamin D (e.g.,25-hydroxyvitamin D₃). The method can further include measuring25-hydroxyvitamin D level in the patient. In one embodiment, the patienthas abnormally elevated PTH levels and normal 25-hydroxyvitamin Dlevels. In another embodiment, the patient has abnormally elevated PTHlevels and abnormally decreased 25-hydroxyvitamin D levels. In yetanother embodiment, the patient has normal PTH levels and abnormallydecreased 25-hydroxyvitamin D levels. The method can further includemeasuring glomerular filtration rate (GFR) in the patient to determinethe stage of the chronic kidney disease.

In one embodiment, and without intending to be bound by any particulartheory, FGF23 level is used as a proxy for CYP24 expression and/oractivity. In another embodiment, and without intending to be bound byany particular theory, elevated FGF23 itself is a marker forsusceptibility to vitamin D deficiency, without respect to anyparticular mechanism of causation (i.e., whether through catabolism byCYP24, or not). The level of FGF23 in a biological sample obtained froma patient can be determined by a variety of techniques known to oneskilled in the art. For example, concentrations of intact FGF-23(iFGF23) and median C-terminal FGF-23 (cFGF23) can be measured usingELISA kits available from IMMUTOPICS (San Clemente, Calif., USA).Measurements of the foregoing species are preferably made as serumconcentrations, although concentrations can be measured in plasma, serumor other bodily fluids (e.g., saliva) or tissues. Normal iFGF23 levelsare in the range of 0 to 90 pg/mL for healthy adult humans (Fliser etal. J. Am. Soc. Nephrol. 18:2601-2608 (2007), Ibrahim et al. Int. Urol.Nephrol. 41(1):163-169 (2009)). Normal cFGF23 levels are in the range of0 to 85 reference units (RU)/mL for healthy adult humans (Tebbin et al.Mayo Clin. Proc. 80(6):745-751(2005)). A level of FGF23 greater than theupper value of the normal range would be indicative of abnormallyelevated CYP24 expression. The further the level of FGF23 is from theupper end of the normal range, the greater the correlation to abnormallyelevated CYP24 expression. Elevated FGF23 according to the methodsdescribed herein will be at least 2-fold greater than normal, forexample 3-fold, 4-fold, 5-fold, 10-fold, 50-fold, 100-fold, or1000-fold.

In another embodiment, CYP24 activity is measured by measuring the levelof one or more catabolic byproducts of CYP24. The level of catabolicbyproducts of CYP24 in a biological sample obtained from a patient canbe determined by a variety of techniques known to one skilled in theart. For example, CYP24 catabolic byproducts can be measured byimmunoassays such as enzyme-linked immunosorbent assays (ELISAs),radioimmunoassays (RIAs), immunofluorescent assays, and the like.Another approach to measure CYP24 byproducts such as 25-hydroxyvitaminD₃-26,23-lactone or 1,25-dihydroxyvitamin D₃-26,23-lactone would takeadvantage of their high affinity to natural vitamin D binding proteinssuch as vitamin D binding protein (DBP) or vitamin D receptor. Suchproteins also can be modified by methods known to one skilled in the artto have greater affinity or selectivity for such vitamin D products.Synthetic antibodies or proteins having affinity for vitamin Dmetabolites of interest could also be generated using techniques such asphage-display or yeast display and could be incorporated into a kit todetermine vitamin D metabolite and CYP24 catabolic byproductconcentration. Other techniques to measure CYP24 catabolic byproductsinclude high performance liquid chromatography (HPLC) in combinationwith UV-visible spectroscopy, fluorescence spectroscopy, massspectrometry, and the like. CYP24 activity also can be measured bymeasuring ratios of one or more catabolic byproducts of CYP24 to one ormore corresponding precursors. CYP24 catabolic byproducts include24-hydroxylated natural and synthetic vitamin D compounds. Examples ofnatural CYP24 catabolic byproducts include 24,25-dihydroxyvitamin D₃,1,24,25-trihydroxyvitamin D₃, 24,25-dihydroxyvitamin D₂, and1,24,25-trihydroxyvitamin D₂. Additional products of CYP24 can also be23-hydroxylated such as the 25-hydroxyvitamin D₃-26,23-lactone or the1,25-dihydroxyvitamin D₃-26,23-lactone. Additional examples of CYP24catabolic byproducts include the products obtained by 24-hydroxylationof synthetic vitamin D compounds. Synthetic vitamin D compounds includeparicalcitol (ZEMPLAR®), doxercalciferol (HECTOROL®), 22-oxacalcitriol,alfacalcidol, and 26,26,26,27,27,27-hexafluorocalcitriol(falecalcitriol). Measurements of the foregoing species are preferablymade as serum concentrations, although concentrations can be measured inserum or other bodily fluids (e.g., saliva). Measurements can be madeafter acute or chronic administration of a CYP24 substrate.

The corresponding precursor compounds of CYP24 catabolic byproductsinclude, for example, 25-hydroxyvitamin D₃, 1,25-dihydroxyvitamin D₃,25-hydroxyvitamin D₂, and 1,25-dihydroxyvitamin D₂. The level ofcorresponding precursor compounds can be measured along with CYP24catabolic byproducts, and ratios of one or more catabolic byproducts ofCYP24 to one or more corresponding precursors can be used to obtain avalue for CYP24 activity. For example, ratios including24,25-dihydroxyvitamin D to 25-hydroxyvitamin D and1,24,25-trihydroxyvitamin D to 1,25-dihydroxyvitamin D can be measuredand used to obtain CYP24 activity. Measurements of the foregoing speciesare preferably made as serum concentrations, although concentrations canbe measured in serum or other bodily fluids (e.g., saliva). Measurementscan be made after acute or chronic administration of a CYP24 substrate.

In another embodiment, CYP24 expression is determined by measuring thelevel of CYP24 mRNA in a patient. The level of mRNA in a biologicalsample obtained from a patient can be determined by a variety oftechniques known to one skilled in the art. In Northern blotting, forexample, mRNA levels can be quantified by hybridizing radioactively- orfluorescently-labeled probes with mRNA samples that have been separatedby electrophoresis and/or bound to a membrane or other solid support.DNA microarray technologies provide another means for quantifying mRNAlevels, whereby a fluorescently-labeled mRNA sample is allowed tohybridize with tens to hundreds of thousands of DNA oligonucleotidesaffixed to a solid support in a defined pattern. Techniques that providesignal amplification are particularly useful when low levels of mRNA arepresent. For example, quantitative real time-polymerase chain reaction(qRT-PCR) provides mRNA quantification by conversion of the target mRNAto the corresponding DNA molecule, followed by amplification via thepolymerase chain reaction. By using a fluorescently labeled primer, mRNAlevels can be monitored in real-time during the amplification process.

In another embodiment, CYP24 expression is determined by measuring thelevel of CYP24 protein in a patient. The level of protein in abiological sample obtained from a patient can be determined by a varietyof techniques known to one skilled in the art. In Western blotting, forexample, protein levels can be quantified by detecting the binding of anantibody specific for the target protein with protein samples that havebeen separated by electrophoresis and/or bound to a membrane or othersolid support. Assays that rely on the binding of a specific antibody toa target antigen (e.g. CYP24) can take a variety of forms, and inaddition to Western blotting (immunoblotting), examples of such assaysinclude enzyme-linked immunosorbent assays (ELISAs), radioimmunoassays(RIAs), immunofluorescent assays, and the like. Protein levels also canbe measured by various staining, spectroscopic, and spectrometricdetection techniques, optionally in combination with various separationtechniques. Examples of detection techniques include Coomassie staining,silver staining, UV-visible spectroscopy, fluorescence spectroscopy,mass spectrometry, and the like. These detection techniques can becombined with separation techniques, such as electrophoresis, capillaryelectrophoresis, high performance liquid chromatography (HPLC), fastprotein liquid chromatography (FPLC), thin layer chromatography (TLC),Luminex® xMAP® multiplexing technology for gene quantification, and thelike.

In yet another embodiment, CYP24 activity is measured by measuring thelevel of CYP24 enzyme activity in a patient. The level of enzymaticactivity in a biological sample obtained from a patient can bedetermined by a variety of techniques known to one skilled in the art.In the case of CYP24, enzymatic activity can be measured by measuringthe conversion of 25-hydroxyvitamin D₃ to the corresponding24-hydroxylated product. For example, conversion of 25-hydroxyvitamin D₃to 24,25-dihydroxyvitamin D₃ can be assessed by incubating a biologicalsample from a patient with a radioactively-labeled 25-hydroxyvitamin D₃substrate, separating the reaction products by HPLC, and measuring theradioactivity of the 24,25-dihydroxyvitamin D₃ peak compared to thetotal radioactivity.

In one aspect, CYP24 expression and/or activity can be measured in oneor more of tissues, plasma, and cells of a vitamin D deficient orvitamin D replete patient. CYP24 expression and/or activity can bemeasured in tissues obtained by a tissue biopsy, and can include tissuessuch as, but not limited to, skin tissue, kidney tissue, liver tissue,parathyroid gland tissue, and the like. In one embodiment, kidney tissueis preferred. In another embodiment, parathyroid gland tissue ispreferred. CYP24 expression and/or activity also can be measured incells, including cells obtained from the blood, such as peripheral bloodmononuclear cells, and cells obtained from swabs of tissues, such asbuccal cells. In one embodiment of the methods herein, CYP24 expressionand/or activity is measured by a systemic indicator (e.g. peripheralblood mononuclear cells or serum), in preference to a tissue-basedmeasurement of overexpression, which can occur in tumor growth.

In one aspect, CYP24 expression and/or activity is abnormally elevated.Normal levels of CYP24 expression and/or activity are defined as 1relative unit (RU) measured based on the mean value of CYP24 expressionand/or activity from 50-100 “normal” donors where CYP24 mRNA has beenprepared and used as a reference.

The basal level for CYP24 can be established from samples (e.g. kidney,skin, blood, serum, plasma, saliva, buccal swab) collected in normalindividuals from various population groups based on, for example,gender, ethnicity, and/or age. CYP24 RNA level can be established fromtissues (e.g. kidney or skin biopsy) or cells (e.g. buccal swab) byreal-time PCR, Luminex® xMAP® multiplexing technology, or anothertechnique. CYP24 protein level will be measured in these tissues byusing techniques such as Luminex® xMAP® multiplexing technology andWestern—blot. The mean value for the CYP24 RNA level or the CYP24protein level will be recorded as 1 RU.

The normal levels of 24-hydroxylated natural and synthetic vitamin Dcompounds such as 24,25-dihydroxyvitamin D₃, 1,24,25-trihydroxyvitaminD₃ or lactones can be established from samples (e.g. blood, plasma,saliva) in absolute quantity based on a standard curve using techniquessuch as HPLC, gas chromatography, mass spectrometry, and methodspreviously cited. The absolute values of the 24-hydroxylated natural andsynthetic vitamin D compounds will be used as the normal levels by thephysician.

If the level of CYP24 RNA, the level of CYP24 protein, or the absolutevalue of a 24-hydroxylated natural or synthetic vitamin D compound in apatient falls outside of the “normal” range, the patient has abnormallyelevated CYP24 expression and/or activity. For example CYP24 expressionand/or activity can be at least 2-fold increased over normal CYP24expression and/or activity, at least 3-fold increased, at least 4-foldincreased, at least 5-fold increased, or at least 10-fold increased overnormal CYP24 expression and/or activity. It is contemplated thatabnormally elevated CYP24 expression and/or activity could be as much ashundreds or thousands of times increased over normal CYP24 expressionand/or activity (e.g., 100×, 500×, 1000×, 5000×, etc.).

In one embodiment, a physician will determine if a patient hasabnormally elevated CYP24 expression and/or activity by collecting atleast one sample (e.g. blood, plasma, saliva, serum, buccal swab) fromthe patient and measuring the level of CYP24 RNA, the level of CYP24protein, or the absolute value of a 24-hydroxylated natural or syntheticvitamin D compound. If one or several measured parameters falls outsideof the “normal” range, and preferably at least 2-fold, 3-fold, 4-foldincreased, etc., as described above, the physician will diagnose thepatient as having abnormally elevated CYP24 activity and/or expressionand may prescribe a CYP24 inhibitor.

CYP24 inhibitors can include organic molecules, single-stranded ordouble-stranded nucleic acids (e.g. sense, anti-sense, or missenseoligonucleotides; aptamers; sense, anti-sense, or missensepolynucleotides; sense, anti-sense, or missense DNA; sense, anti-sense,or missense RNA; and siRNA), peptides, carbohydrates, and proteins (e.g.antibodies, antibody fragments, hormones, hormone analogs,glycoproteins, and lectins). In one embodiment, the CYP24 inhibitorcomprises the compound disclosed as Formula IX (Compound 1) in U.S. Pat.No. 6,380,408 (col. 6), which is(5Z,7E,16Z,23E)-(1S,3R)-25-nor-25-t-butylsulfonyl-9,10-seco-5,7,10(19),16,23-cholestapentaene-1,3-diol.In another embodiment, the CYP24 inhibitor comprises an azole compoundsuch as, for example,(R)-N-(2-(1H-imidazol-1-yl)-2-phenylethyl)-4′-chlorobiphenyl-4-carboxamide,ketoconazole, metronidazole, clomethiazole, itraconazole, andfluconazole.

One class of organic molecule inhibitors of CYP24 includes analogs ofvitamin D compounds. Examples of 1α,25-dihydroxyvitamin D₃ analogs whichhave CYP-24 inhibition activity are disclosed in U.S. Pat. Nos.6,380,408; 7,101,865; 7,166,585; and 6,982,258, and U.S. patentapplication Ser. No. 10/738,248, incorporated herein by reference intheir entirety, and include 23,23-difluoro-24-sulfone vitamin D₃compounds, 25-sulfone vitamin D₃ compounds, 24,24-difluoro-25-sulfonevitamin D₃ compounds, 24-sulfoximine vitamin D₃ compounds,16-ene-25-oxime vitamin D₃ compounds, and 16-ene-25-oxime ether vitaminD₃ compounds, 24-sulfone vitamin D₃ compounds, and 24,24-difluorovitamin D₃ compounds. In one aspect of the method, the molecule can beselected from pure CYP24 inhibitors, for example(5Z,7E)-(1S,3R)-24-(S)-phenylsulfoximine-25-nor-9,10-seco-5,7,10(19)-cholestatriene-1,3-diol(see U.S. Pat. No. 7,101,865, Compound I(a)). In another aspect of themethod, the molecule can be selected from compounds which are both CYP24inhibitors and vitamin D agonists, for example(5Z,7E,16Z,23E)-25-nor-25-t-butylsulfonyl-9,10-seco-5,7,10(19),16,23-cholestapentaene-1,3β-diol(see U.S. Pat. No. 6,380,408, Formula IX, Compound 1) and(5Z,7E,16Z)-(1S,3R)-25-(O-allyl)-N-t-butyloxime-9,10-seco-5,7,10(19),16-cholestatetraene-1,3β-diol(see U.S. Pat. No. 6,982,258, Compound I(g)).

CYP24 inhibitors optionally can be administered in combination withother agents that increase vitamin D levels in the body. Agents known inthe art to increase vitamin D levels in the body are encompassed by thepresent disclosure and include, for example, vitamin D₂,25-hydroxyvitamin D₂, 1,25-dihydroxyvitamin D₂, vitamin D₃,25-hydroxyvitamin D₃, and 1,25-dihydroxyvitamin D₃. Preferably, activevitamin D compounds are avoided in favor of vitamin D prehormones,vitamin D prohormones, and analogs thereof.

Both cholecalciferol and ergocalciferol are metabolized into prohormonesby enzymes primarily located in the liver of the human body.Cholecalciferol is metabolized into a prohormone 25-hydroxyvitamin D₃,and ergocalciferol is metabolized into two prohormones,25-hydroxyvitamin D₂ and 24(S)-hydroxyvitamin D₂. Cholecalciferol andergocalciferol also can be metabolized into prohormones outside of theliver in certain cells, such as enterocytes, by enzymes which areidentical or similar to those found in the liver. Elevatingconcentrations of either precursor increases prohormone production;similarly, lowering precursor concentrations decreases hormoneproduction. Surges in the blood levels of cholecalciferol and/orergocalciferol (“cholecalciferol/ergocalciferol”) can transiently raiseintracellular Vitamin D concentrations, accelerating prohormoneproduction and elevating intracellular and blood prohormoneconcentrations.

Blood levels of 1,25-dihydroxyvitamin D are precisely regulated by afeedback mechanism which involves PTH. The renal 1α-hydroxylase (orCYP27B1) is stimulated by PTH and inhibited by 1,25-dihydroxyvitamin D.When blood levels of 1,25-dihydroxyvitamin D fall, the parathyroidglands sense this change via intracellular vitamin D receptors andsecrete PTH. The secreted PTH stimulates expression of renal CYP27B1and, thereby, increases production of vitamin D hormones. As bloodconcentrations of 1,25-dihydroxyvitamin D rise again, the parathyroidglands attenuate further PTH secretion. As blood PTH levels fall, renalproduction of vitamin D hormones decreases. Rising blood levels of1,25-dihydroxyvitamin D also directly inhibit further vitamin D hormoneproduction by CYP27B1.

Substantial surges in the blood levels of cholecalciferol,ergocalciferol, and 25-hydroxyvitamin D also can cause up-regulation ofCYP24 as a response, to catabolize the transitory excess of vitamin Dsubstrates. Similarly, rising blood levels of 1,25-dihydroxyvitamin Dcan cause up-regulation of CYP24 activity.

Without intending to be bound by any particular mode of operation, it isbelieved that overexpression of CYP24 is the cause of at least someforms of vitamin D deficiency, operating independently of, butpotentially complicated by, deficiencies in substrates and/or sunlight.

Accordingly, in one type of embodiment of the methods disclosed herein,a CYP24 inhibitor will be administered alone, or without administrationof a vitamin D compound (e.g. cholecalciferol, ergocalciferol, vitamin Dprohormone, vitamin D hormone, or analogs thereof), most preferablywithout administration of an active vitamin D hormone or analog thereof.In another embodiment of the methods disclosed herein, a CYP24 inhibitorwill be administered alone, or when a vitamin D compound (e.g.cholecalciferol, ergocalciferol, vitamin D prohormone, vitamin Dhormone, or analogs thereof) is also administered, the vitamin Dcompound will be administered in a modified release formulation to avoidsurges in blood levels of the compound (e.g. a sustained or extendedrelease formulation), or via a slow-push IV delivery method.

In one aspect, the present disclosure provides a kit for diagnosingcatabolism-related vitamin D deficiency. The kits in accordance with thepresent disclosure provide a measure of CYP24 expression and/oractivity, and include kits measuring one or more properties includinglevels of CYP24 catabolic byproducts or precursors to the catalyticbyproducts, levels of CYP24 mRNA, levels of CYP24 protein, and/or levelsof CYP24 enzyme activity. In one embodiment, the kit includes animmobilized anti-CYP24 antibody, a labeled anti-CYP24 antibody, andinstructions for use, for example according to a method disclosedherein. Other kits involving antibody-based detection are alsocontemplated by the present disclosure. For example, kits for measuringCYP24 expression can measure the level of CYP24 catabolic byproducts.The kits can include an assay for measuring the levels of one or morecorresponding precursors to the catalytic byproducts. One such kit caninclude an antibody (or functional fragments thereof) specific for aCYP24 catabolic byproduct, and an antibody specific for vitamin Dcompounds including CYP24 catabolic byproducts. Proteins with highaffinity for vitamin D metabolites and CYP24 catabolic byproducts suchas DBP or VDR or synthetically derived proteins or macromolecules canalso be contemplated for use in place of the antibody in such kits. Itis contemplated that one of the aforementioned antibodies is immobilizedto a solid support and the other antibody possesses a label fordetection. In another example, a kit for measuring CYP24 expression caninclude an immobilized CYP24 catabolic byproduct, and an anti-CYP24antibody. CYP24 activity is measured with the aforementioned kit bymeasuring the ability of CYP24 catabolic byproducts to compete with theimmobilized CYP24 catabolic byproduct for binding to the anti-CYP24antibody.

In another aspect, the disclosure includes a pharmaceutical formulationfor treating or preventing vitamin D deficiency including an effectiveamount of a CYP24 inhibitor. The formulation can further include aneffective amount of 25-hydroxyvitamin D₃.

In yet another aspect, the disclosure includes a pharmaceuticalformulation for treating or preventing hyperparathyroidism including aneffective amount of a CYP24 inhibitor. The formulation can furtherinclude an effective amount of 25-hydroxyvitamin D₃. The pharmaceuticalformulation can be for treating hyperparathyroidism secondary to ChronicKidney Disease, for example Stage 1 or Stage 2 CKD.

The exact formulation, route of administration, and dosage is determinedby an individual physician in view of the patient's condition. Dosageamounts and intervals can be adjusted individually to provide levels ofthe active ingredients that are sufficient to maintain therapeutic orprophylactic effects.

Such formulations can be in the form of, for example, granules, powders,tablets, capsules, syrup, suppositories, injections, emulsions, elixirs,suspensions or solutions. The instant formulations can be formulated forvarious routes of administration, for example, by oral administration,by nasal administration, by rectal administration, subcutaneousinjection, intravenous injection, intramuscular injections, orintraperitoneal injection. The following dosage forms are given by wayof example and should not be construed as limiting the instantinvention.

For oral, buccal, and sublingual administration, powders, suspensions,granules, tablets, pills, capsules, gelcaps, and caplets are acceptableas solid dosage forms. These can be prepared, for example, by mixing oneor more of the CYP24 inhibitors or dual action CYP24 inhibitor and VDRagonist of the instant invention with at least one additive such as astarch or other additive. Suitable additives are sucrose, lactose,cellulose sugar, mannitol, maltitol, dextran, starch, agar, alginates,chitins, chitosans, pectins, tragacanth gum, gum arabic, gelatins,collagens, casein, albumin, synthetic or semi-synthetic polymers orglycerides. Optionally, oral dosage forms can contain other ingredientsto aid in administration, such as an inactive diluent, or lubricantssuch as magnesium stearate, or preservatives such as paraben or sorbicacid, or anti-oxidants such as ascorbic acid, tocopherol or cysteine, adisintegrating agent, binders, thickeners, buffers, sweeteners,flavoring agents or perfuming agents. Tablets and pills may be furthertreated with suitable coating materials known in the art.

Liquid dosage forms for oral administration may be in the form ofpharmaceutically acceptable emulsions, syrups, elixirs, suspensions, andsolutions, which may contain an inactive diluent, such as water.Pharmaceutical formulations and medicaments may be prepared as liquidsuspensions or solutions using a sterile liquid, such as, but notlimited to, an oil, water, an alcohol, and combinations of these.Pharmaceutically suitable surfactants, suspending agents, emulsifyingagents, may be added for oral or parenteral administration.

As noted above, suspensions may include oils. Such oil include, but arenot limited to, peanut oil, sesame oil, cottonseed oil, corn oil andolive oil. Suspension preparation may also contain esters of fatty acidssuch as ethyl oleate, isopropyl myristate, fatty acid glycerides andacetylated fatty acid glycerides. Suspension formulations may includealcohols, such as, but not limited to, ethanol, isopropyl alcohol,hexadecyl alcohol, glycerol and propylene glycol. Ethers, such as butnot limited to, poly(ethyleneglycol), petroleum hydrocarbons such asmineral oil and petrolatum; and water may also be used in suspensionformulations.

For nasal administration, the pharmaceutical formulations andmedicaments may be a spray or aerosol containing an appropriatesolvent(s) and optionally other compounds such as, but not limited to,stabilizers, antimicrobial agents, antioxidants, pH modifiers,surfactants, bioavailability modifiers and combinations of these. Apropellant for an aerosol formulation may include compressed air,nitrogen, carbon dioxide, or a hydrocarbon based low boiling solvent.

Injectable dosage forms generally include aqueous suspensions or oilsuspensions which may be prepared using a suitable dispersant or wettingagent and a suspending agent. Injectable forms may be in solution phaseor in the form of a suspension, which is prepared with a solvent ordiluent. Acceptable solvents or vehicles include sterilized water,Ringer's solution, or an isotonic aqueous saline solution.Alternatively, sterile oils may be employed as solvents or suspendingagents. Preferably, the oil or fatty acid is non-volatile, includingnatural or synthetic oils, fatty acids, mono-, di- or tri-glycerides.

For injection, the pharmaceutical formulation and/or medicament may be apowder suitable for reconstitution with an appropriate solution asdescribed above. Examples of these include, but are not limited to,freeze dried, rotary dried or spray dried powders, amorphous powders,granules, precipitates, or particulates. For injection, the formulationsmay optionally contain stabilizers, pH modifiers, surfactants,bioavailability modifiers and combinations of these.

For rectal administration, the pharmaceutical formulations andmedicaments may be in the form of a suppository, an ointment, an enema,a tablet or a cream for release of compound in the intestines, sigmoidflexure and/or rectum. Rectal suppositories are prepared by mixing oneor more compounds of the instant invention, or pharmaceuticallyacceptable salts or tautomers of the compound, with acceptable vehicles,for example, cocoa butter or polyethylene glycol, which is present in asolid phase at normal storing temperatures, and present in a liquidphase at those temperatures suitable to release a drug inside the body,such as in the rectum. Oils may also be employed in the preparation offormulations of the soft gelatin type and suppositories. Water, saline,aqueous dextrose and related sugar solutions, and glycerols may beemployed in the preparation of suspension formulations which may alsocontain suspending agents such as pectins, carbomers, methyl cellulose,hydroxypropyl cellulose or carboxymethyl cellulose, as well as buffersand preservatives.

The formulations of the invention may be designed to be short-acting,fast-releasing, long-acting, and sustained-releasing as described below.Thus, the pharmaceutical formulations may also be formulated forcontrolled release or for slow release.

The instant compositions may also comprise, for example, micelles orliposomes, or some other encapsulated form, or may be administered in anextended release form to provide a prolonged storage and/or deliveryeffect. Therefore, the pharmaceutical formulations and medicaments maybe compressed into pellets or cylinders and implanted intramuscularly orsubcutaneously as depot injections or as implants such as stents. Suchimplants may employ known inert materials such as silicones andbiodegradable polymers.

Specific dosages may be adjusted depending on conditions of disease, theage, body weight, general health conditions, sex, and diet of thesubject, dose intervals, administration routes, excretion rate, andcombinations of drugs. Any of the above dosage forms containingeffective amounts are well within the bounds of routine experimentationand therefore, well within the scope of the instant invention.

Besides those representative dosage forms described above,pharmaceutically acceptable excipients and carries are generally knownto those skilled in the art and are thus included in the instantinvention. Such excipients and carriers are described, for example, in“Remingtons Pharmaceutical Sciences” Mack Pub. Co., New Jersey (1991),which is incorporated herein by reference.

Suitable modified release formulations for vitamin D compounds aredisclosed in application PCT/US2008/061579, published as WIPOpublication WO 2008/134512 (Nov. 6, 2008), and the disclosure thereof isincorporated herein by reference. It is contemplated that suchformulations can also include compatible CYP24 inhibitors anddual-action CYP23 inhibitors and VDR agonists.

EXAMPLES

The following examples are provided for illustration and are notintended to limit the scope of the invention.

The Examples below support the following conclusions.

CYP24 gene expression is strongly induced by 1,25-dihydroxyvitamin D₃ intissues from both normal and uremic rats.

Constitutive expression of CYP24 is relatively higher in healthy kidneycompared to other tissues. In uremic rats, however, basal expression ofCYP24 is markedly elevated. This suggests that mechanisms associatedwith the uremic state may be involved in regulating CYP24 expression.

CYP24 is significantly induced by 1,25-dihydroxyvitamin D₃ inparathyroid glands of uremic animals compared to those from normalanimals, suggesting that repeated dosing may lead to increasedresistance.

Expression of CYP27B1 in uremic rats does not correlate with diminishedlevels of 1,25-dihydroxyvitamin D₃, suggesting a more prominent role forCYP24 in lowering vitamin D levels in uremia.

In normal animals, CYP24 expression is dependent upon vitamin D status;vitamin D deficiency markedly decreases CYP24 expression levels. Uremicanimals exhibit higher basal levels of CYP24 expression which do notchange in a state of vitamin D deficiency. This suggests that in uremia,mechanisms independent of vitamin D regulate CYP24 levels. This may havean impact on vitamin D status in uremia.

Elevated basal expression of CYP24 in the uremic kidney may be asignificant mechanism contributing to underlying 25(OH)D₃ and1,25-dihydroxyvitamin D₃ deficiency and resistance to vitamin D hormonereplacement therapy. Compounds which inhibit CYP24 may be useful inmaintaining vitamin D status and overcoming CYP24 resistance to therapy.

FGF23 synergizes with 1,25-dihydroxyvitamin D to induce CYP24 RNAproduction. In a uremic situation, a high level of FGF23 mightcontribute to further elevate CYP24, making a patient resistant tovitamin D treatment.

CYP24 levels decrease in vitamin D deficient animals and increase tonormal or higher levels after treatment with 25-hydroxyvitamin D.

CYP24 levels do not change in uremic vitamin D deficient rats and do notincrease after treatment with 25-hydroxyvitamin D, which suggests a lossof vitamin D control in uremic rats.

In vitamin D deficient uremic rats, CYP24 RNA levels are elevatedcompared to vitamin D deficient animals. This can explain why, afterdosing with 25-hydroxyvitamin D₃ for two weeks, the levels of1,25-dihydroxyvitamin D₃ are lower in vitamin D deficient uremic ratscompared to vitamin D deficient animals.

Example 1 Animal Model of Vitamin D Deficiency

To obtain an animal model of vitamin D deficiency, rats were fed anadenine-rich diet. After 7 days, elevated parathyroid hormone (PTH)levels were observed by an intact PTH (iPTH) Elisa Kit in adenine-fedanimals compared to control-diet animals, and after 29 days, secondaryhyperparathyroidism had developed in adenine-fed animals, but not inanimals receiving the control diet (FIG. 1). iPTH level wassignificantly reduced by treatment of adenine-fed animals with vitamin Dcompounds. As shown in FIG. 2, iPTH level in adenine-fed animals wasrestored to a level similar to control-fed animals by treating theadenine-fed animals with 1,25-(OH)₂-D₃ (calcitriol or1,25-dihydroxyvitamin D₃), 25-OH-D₃ (calcidiol or 25-hydroxyvitamin D₃),or 1,25-(OH)₂-D₂ (1,25-dihydroxyvitamin D₂).

Vitamin D hormone status of the adenine-fed and control animals wasassessed by measuring the level of 1,25-(OH)₂-D₃ (calcitriol or1,25-dihydroxyvitamin D₃), the active form of vitamin D by massspectrometry. Adenine-fed animals displayed a reduction in vitamin Dhormone status compared to animals fed a control diet (FIG. 3). VitaminD status in adenine-fed animals was restored to the level of control-fedanimals by treating the adenine-fed animals with 1,25-(OH)₂-D₃. Incontrast, treatment of adenine-fed animals with 25-OH-D₃ (calcidiol or25-hydroxyvitamin D₃) or 1,25-(OH)₂-D₂ (1,25-dihydroxyvitamin D₂) didnot significantly affect the 1,25-(OH)₂-D₃ levels of these animals (FIG.3).

Example 2 CYP24 Expression in Vitamin D Deficiency

To determine the relationship between vitamin D deficiency and CYP24level, CYP24 expression was measured by qRT-PCR in adenine-fed rats andcontrol-diet-fed animals. In kidney tissue of adenine-fed animals, CYP24expression was abnormally elevated approximately 7-fold compared tokidney tissue of control-diet fed animals (FIG. 4). Treatment ofadenine-fed animals with vitamin D compounds further induced CYP24. Asshown in FIG. 4, treatment of adenine-fed rats with 1,25-(OH)₂-D₃(calcitriol or 1,25-dihydroxyvitamin D₃), 25-OH-D₃ (calcidiol or25-hydroxyvitamin D₃), or 1,25-(OH)₂-D₂ (1,25-dihydroxyvitamin D₂)resulted in 2-fold to 25-fold elevation of CYP24 expression activity. Inparathyroid gland tissue of adenine-fed animals, CYP24 expressionactivity was abnormally elevated approximately 3-fold compared toparathyroid gland tissue of control-diet fed animals (FIG. 5). Treatmentof adenine-fed animals with vitamin D compounds dramatically inducedCYP24. As shown in FIG. 5, treatment of adenine-fed rats with1,25-(OH)₂-D₃ (calcitriol or 1,25-dihydroxyvitamin D₃), 25-OH-D₃(calcidiol or 25-hydroxyvitamin D₃), or 1,25-(OH)₂-D₂(1,25-dihydroxyvitamin D₂) resulted in 50-fold to 14,000-fold elevationof CYP24 expression activity.

Example 3 FGF23 Expression in Vitamin D Deficiency

To determine the relationship between vitamin D deficiency andfibroblast growth factor-23 (FGF23) level, serum FGF23 level wasmeasured in adenine-fed rats and control-diet fed animals. Inadenine-fed animals, serum FGF23 level was abnormally elevated at least53-fold compared to control-diet fed animals (FIG. 6). Adenine-fedanimals treated with vitamin D compounds also showed elevated levels ofFGF23. As shown in FIG. 6, treatment of adenine-fed rats with1,25-(OH)₂-D₃ (calcitriol or 1,25-dihydroxyvitamin D₃), 25-OH-D₃(calcidiol or 25-hydroxyvitamin D₃), or 1,25-(OH)₂-D₂(1,25-dihydroxyvitamin D₂) resulted in at least 74-fold elevation ofFGF23 levels compared to control-diet fed animals.

Levels of FGF23 and osteoclacin, a biomarker for bone formation, weremeasured in kidney tissue from adenine-fed rats and control-diet fedanimals. FGF23 was elevated approximately 55-fold and osteoclacin waselevated approximately 1.5-fold in adenine-fed animals compared tocontrol-diet animals (FIG. 7).

Example 4 CYP24 Expression in 25-Hydroxyvitamin D Treatment

FIG. 8 shows a graph of relative CYP24 induction in rats treated withvitamin D (25-hydroxyvitamin D₂ and 25-hydroxyvitamin D₃) for 2 weeks.Normal rats were intravenously administered 16 μg/kg 25-hydroxyvitaminD₂, 25-hydroxyvitamin D₃, and a control vehicle for 2 weeks, Blood wascollected and CYP24 expression was measured by real-time PCR.

Example 5

The effect of5Z,7E,16Z,23E)-(1S,3R)-25-nor-25-t-butylsulfonyl-9,10-seco-5,7,10(19),16,23-cholestapentaene-1,3-diolon 25-hydroxyvitamin D levels was assessed in human subjects. Subjectswere dosed with placebo or the compound on days 1, 3, 5, 8, and 10.Twenty-four hours after the last dose of the compound, 25-hydroxyvitaminD level was measured. The percent change in serum 25-hydroxyvitamin D isshown in FIG. 9 (p=0.1 for both 90 mcg and 180 mcg).

Example 6

Sprague-Dawley rats were treated i.v. daily with vehicle or 0.5 mcg/kg1,25-dihydroxyvitamin D₃ for 1 week. Organs were collected 24 hoursafter the last dosing. CYP24 gene expression was determined by real-timePCR. The results are shown in FIG. 10.

Sprague-Dawley rats were fed a standard diet (normal) or auremia-inducing diet containing 0.75% adenine (uremic) for 4 weeks.Animals were then dosed i.v. daily with vehicle or 0.5 mcg/kg1,25-dihydroxyvitamin D₃ for 7 days. Organs were collected 24 hoursafter the final dosing. CYP24 gene expression was determined byreal-time PCR and normalized to GAPDH levels. Relative expression valuesare normalized to the vehicle-treated group (relative expression=1). Theresults are shown in FIG. 11.

FIGS. 10 and 11 show that basal expression of CYP24 is significantlyelevated in kidney (FIG. 10), but not parathyroid gland (FIG. 11), inthe uremic rat compared to the normal rat. However, induced expressionof CYP24 by 1,25-dihydroxyvitamin D₃ (1α,25(OH)₂D₃) is markedly greaterin parathyroid gland from uremic compared to normal animals. “*” denotesa significant difference in CYP24 expression between vehicle and1,25-dihydroxyvitamin D₃ treatment in normal and uremic rats. “**”represents a significant difference between vehicle-treated normal anduremic rats. “†” denotes significant difference in CYP24 inductionlevels between normal and uremic rats treated with 1,25-dihydroxyvitaminD₃. Significance was set at a p value cutoff of <0.05. Data arepresented as mean±SEM. Numerals above each bar signifies relative foldinduction to normal-vehicle.

Example 7

CYP24 and CYP27B1 expression was measured using the same protocoloutlined above in Example 6 with respect to FIG. 11. Serum levels of25(OH)D₃ and 1,25-dihydroxyvitamin D₃ were measured by LC-MS. Serum PTHwas measured by ELISA IMMUTOPICS (San Clemente, Calif., USA) accordingto manufacturer's instructions. Briefly, serum samples were spiked with[26,27-²H₆]25(OH)D₃ or [25,26-²H₆]1,25-dihydroxyvitamin D₃ and dissolvedin acetonitrile to serve as an internal standard. 1,25-dihydroxyvitaminD₃ or 25(OH)D₃ and internal standards were extracted from serum usingAccubond II ODS-C18 100 mg, 1 mL SPE cartridges (Agilent Technologies).The collected fractions were evaporated to dryness under a steady streamof nitrogen gas and the residues reconstituted in 50 μL of methanol/H₂O(80/20; v/v) and analyzed using LC-MS/MS (Waters Alliance HPLC-WatersQuattro Ultima mass spectrometer). Relative expression values arenormalized to the vehicle-treated group (relative expression=1). Theresults are shown in FIG. 12.

FIG. 12 shows that increased basal CYP24 expression, in the absence ofchanges to CYP27B1, may contribute to lower levels of1,25-dihydroxyvitamin D₃ in uremic rats. Treatment with1,25-dihydroxyvitamin D₃ causes a reduction in serum 25-(OH)D₃ levels.Treatment with 1,25-dihydroxyvitamin D₃ causes a reduction in PTH, butalso drastically induces CYP24 expression. Asterisk represents astatistically significant difference between normal and uremic groupsfor CYP27B1 (*) and CYP24 (**). In the upper panel, (*) denotes asignificant difference in vitamin D levels between normal and uremicrats. Statistical significance was determined using student'sindependent t test with p value cut off of <0.05. Data are presented asmean±SEM.

Example 8

Vitamin D deficiency was induced in Sprague-Dawley rats by feeding adiet lacking vitamin D for 6 weeks. Normal rats were fed a standard dietcontaining vitamin D. Uremia was induced by oral administration (gavage)of 0.2% adenine solution for the last 2 weeks. Non-uremic controls ratswere administered vehicle by oral gavage. Serum and organs werecollected 24 hours after the last dose of adenine. Gene expression wasdetermined by real-time PCR. Measurement of serum levels of 25(OH)D₃ and1,25-dihydroxyvitamin D₃ is detailed above with respect to Example 7.The results are shown in FIG. 13.

FIG. 13 shows that increased basal expression of CYP24 is not dependenton vitamin D metabolite levels in uremic rats. “*” denotes a significantdifference between groups relative to non-uremic normal. “**” representsa significant difference between CYP27B1 normal and CYP27B1 vitamin Ddeficient (VD Def) diet. Statistical significance was determined usingstudent's independent t test with p value cut off of <0.05. Data arepresented as mean±SEM. Non-detectable levels are designated as “ND.”

Example 9

HEK cells were seeded at 25,000 cells per well (24-well plate) andincubated with 1,25-dihydroxyvitamin D₃ (10 nM) alone or with a CYP24inhibitor (MK-24(S)-S(0)(NH)-Ph-1, see U.S. Pat. No. 7,101,865, compound1(a)) (10 nM) for 6, 24, 48 and 72 hours, Cells were collected and RNAwas prepared using TRIZOL® reagent. CYP24 was quantified using real-timePCR. The results are shown in FIG. 14.

The results show that CYP24 induction is markedly extended by1,25-dihydroxyvitamin D₃ in the presence of CYP24 inhibitorMK-24(S)-S(O)(NH)-Ph-1.

Example 10

HEK cells were transferred into 96-well plates at 2000 cells/welldensity. After 2 days of growth in 96-well plates the cells were treatedwith 1,25-dihydroxyvitamin D₃ at the final concentrations 10⁻⁶-10⁻¹¹ Min combination with the MK-24(S)-S(O)(NH)-Ph-1 compound with the variedfinal concentration of 0, 1, 10 and 50 nM. After overnight treatment[³H]-thymidine was added to cells, 0.2 mCi/well in KGM media for 16 h.The radioactivity incorporation was counted using a scintillationcounter after the addition of 25 ml of scintillation fluid. The resultsare shown in FIG. 15. The data were represented as an incorporation ofthymidine in cpm depending on 1,25-dihydroxyvitamin D₃ concentration.Each data point represents at least 4 independent trials.

The results show that inhibition of CYP24 activity enhances theanti-proliferative effects of 1,25-dihydroxyvitamin D₃ in cultured HEKcells approximately 3 orders of magnitude.

Example 11

HPK1a-ras cells were treated with 0, 1, 10, and 100 nM of1,25-dihydroxyvitamin D₃ (calcitriol), with or without 100 ng/mL ofFGF23, and CYP24 RNA expression was measured after 8 hours. The resultsshow that the presence of FGF23 synergizes with 1,25-dihydroxyvitamin D₃to induce CYP24 RNA production (FIG. 16).

Example 12

Sprague Dawley rats were fed either a normal diet or a vitamin Ddeficient diet for a period of four weeks. Animals were then injecteddaily for two weeks with either 25-hydroxyvitamin D₃ at 0.6, 3, or 18mcg/kg or vehicle as per the axis label in FIG. 17. Kidneys werecollected 24 hours after the last injection and CYP24 mRNA levels weremeasured by real-time PCR. Results are shown in FIG. 17.

Example 13

Sprague Dawley rats were fed either a normal diet (Adenine Vehiclegroup) or a vitamin D deficient diet (Vit. D def./Adenine Vehicle group)for a period of four weeks. Following this treatment, animals wereorally administered, daily for two weeks, 100 mg of adenine. Animalswere then injected daily for another two weeks with either25-hydroxyvitamin D₃ at 0.6 or 18 mcg/kg or vehicle as per the axislabel in FIG. 18. Kidneys were collected 24 hours after the lastinjection and CYP24 mRNA levels were measured by real-time PCR. Resultsare shown in FIG. 18.

Example 14

FIG. 19 shows the levels of 1,25-dihydroxyvitamin D₃ in vitamin Ddeficient uremic rats compared to vitamin D deficient rats that weredosed with 6 or 18 mcg/kg of 25-hydroxyvitamin D for two weeks.

The foregoing description is given for clearness of understanding only,and no unnecessary limitations should be understood therefrom, asmodifications within the scope of the invention may be apparent to thosehaving ordinary skill in the art.

Throughout the specification, where compositions are described asincluding components or materials, it is contemplated that thecompositions can also consist essentially of, or consist of, anycombination of the recited components or materials, unless describedotherwise.

The practice of a method disclosed herein, and individual steps thereof,can be performed manually and/or with the aid of electronic equipment.Although processes have been described with reference to particularembodiments, a person of ordinary skill in the art will readilyappreciate that other ways of performing the acts associated with themethods may be used. For example, the order of various of the steps maybe changed without departing from the scope or spirit of the method,unless described otherwise. In addition, some of the individual stepscan be combined, omitted, or further subdivided into additional steps.

In jurisdictions that forbid the patenting of methods that are practicedon the human body, the meaning of “ administering” of a composition to ahuman subject shall be restricted to prescribing a controlled substancethat a human subject will self-administer by any technique (e.g.,orally, inhalation, topical application, injection, insertion, etc.).The broadest reasonable interpretation that is consistent with laws orregulations defining patentable subject matter is intended. Injurisdictions that do not forbid the patenting of methods that arepracticed on the human body, the “administering” of compositionsincludes both methods practiced on the human body and also the foregoingactivities.

All patents, publications and references cited herein are hereby fullyincorporated by reference. In case of conflict between the presentdisclosure and incorporated patents, publications and references, thepresent disclosure should control.

1. A method of diagnosing a susceptibility for catabolism-relatedvitamin D deficiency in a patient, comprising: measuring a patient'slevel of CYP24 expression and/or activity, or a proxy indicativethereof, by obtaining a tissue, blood, or cell sample from a patient andassaying the sample for CYP24 expression and/or activity, or a proxyindicative thereof, wherein abnormally elevated CYP24 expression and/oractivity indicates a susceptibility for catabolism-related vitamin Ddeficiency.
 2. The method according to claim 1, wherein the patient isvitamin D replete, and further comprising inhibiting and/or preventingvitamin D deficiency by administering a CYP24 inhibitor to the patientin response to abnormally elevated CYP24 expression and/or activity. 3.The method according to claim 1, wherein the patient is vitamin Ddeficient, and further comprising treating the vitamin D deficiency byadministering a CYP24 inhibitor to the patient in response to abnormallyelevated CYP24 expression and/or activity.
 4. A method of diagnosing andtreating a patient, comprising: measuring a patient's CYP24 expressionand/or activity, or a proxy indicative thereof; and administering aCYP24 inhibitor to the patient in response to abnormally elevated CYP24expression and/or activity.
 5. The method of claim 4, further comprisingobtaining a tissue, blood, or cell sample from the patient and assayingthe sample for CYP24 expression and/or activity, or a proxy indicativethereof.
 6. The method of claim 1, wherein, at the time of saidmeasurement, the patient is not undergoing active vitamin D therapy. 7.The method according to claim 1, wherein the patient does not havecancer.
 8. The method according to claim 4, further comprising measuringthe patient's 25-hydroxy vitamin D levels and treating vitamin Ddeficiency by administering the CYP24 inhibitor to a vitamin D deficientpatient.
 9. The method according to claim 8, further comprisingadministering to the patient one or more of vitamin D prehormones,prohormones, and analogs of any of the foregoing
 10. The method of claim9, wherein said therapy comprises administration of a compound selectedfrom cholecalciferol, ergocalciferol, 25-hydroxy vitamin D₂,25-hydroxyvitamin D₃, and combinations thereof.
 11. The method of claim10, wherein said therapy comprises administration of 25-hydroxyvitaminD₃.
 12. The method of claim 11, wherein said therapy comprisesadministration of a therapeutically effective amount of25-hydroxyvitamin D₃ to restore the patient's 25-hydroxy vitamin Dlevels to at least 30 ng/niL.
 13. The method according to claim 4,further comprising measuring the patient's 25-hydroxyvitamin D levelsand inhibiting and/or preventing vitamin D deficiency by administeringthe CYP24 inhibitor to a vitamin D replete patient.
 14. The methodaccording to claim 4, wherein the patient has Chronic Kidney Disease.15. The method according to claim 14, wherein the Chronic Kidney Diseaseis Stage 1 or Stage
 2. 16. The method according to claim 14, wherein theChronic Kidney Disease is Stage 3 or Stage
 4. 17. The method accordingto claim 4, wherein said patient has hyperparathyroidism.
 18. The methodaccording to claim 14, wherein the patient's PTH level is above thetarget range for the patient's Stage of CKD.
 19. The method according toclaim 4, wherein the patient has a deficiency in 1,25-dihydroxy vitaminD₃.
 20. The method according to claim 4, further comprising avoidingactive vitamin D therapy or reducing the level of or omitting activevitamin D therapy if the patient is undergoing active vitamin D therapy.21. The method according to claim 20, further comprising administering25-hydroxy vitamin D to the patient in an amount sufficient to increase1,25-dihydroxy vitamin D levels.
 22. The method according to claim 21,wherein the CYP24 inhibitor is also a vitamin D receptor agonist. 23.The method according to claim 1, comprising measuring the level of FGF23in the patient as a proxy for the level of CYP24 expression and/oractivity, wherein a level of FGF23 greater than the upper value of thenormal range indicates abnormally elevated CYP24 expression.
 24. Themethod according to claim 23, wherein a level of FGF23 at least twotimes greater than the upper value of the normal range indicatesabnormally elevated CYP24 expression.
 25. The method according to claim1, comprising measuring the concentration of one or more catabolicbyproducts of CYP24 in serum or another bodily fluid as a proxy forCYP24 activity.
 26. The method according to claim 25, further comprisingmeasuring the concentration of one or more precursors to the one or morecatabolic byproducts of CYP24 in serum or another bodily fluid andcalculating a ratio of concentrations of one or more catabolicbyproducts of CYP24 to serum concentrations of one or more correspondingprecursors as a proxy for CYP24 activity.
 27. The method according toclaim 26, wherein the catabolic byproducts of CYP24 include one or bothof 24,25-dihydroxyvitamin D and 1,24,25-tnhydroxy vitamin D.
 28. Themethod according to claim 26, wherein the measuring of CYP24 activitycomprises measuring one or more ratios selected from the groupconsisting of 24,25-dihydroxyvitamin D to 25-hydroxy vitamin D and1,24,25-trihydroxyvitamin D to 1,25-dihydroxy vitamin D.
 29. The methodaccording to claim 25, wherein the catabolic byproducts of CYP24 includethe 24-hydroxylated and/or 23-hydroxylated catabolic byproducts of oneor more members selected from the group consisting of paricalcitol,doxercalciferol, 22-oxacalcitriol, dihydrotachysterol, and26,26,26,27,27,27-hexafluorocalcitriol. (falecalcitriol).
 30. The methodaccording to claim 25, wherein the measuring follows acute or chronicadministration of a CYP24 substrate.
 31. The method according to claim25, wherein one or more measurements comprise serum concentrations. 32.The method according to claim 1, wherein the measuring of CYP24expression comprises measuring CYP24 mRNA in tissues, plasma, or cells.33. The method according to claim 1, wherein the measuring of CYP24expression comprises measuring CYP24 protein in tissues, plasma, orcells.
 34. The method according to claim 1, wherein the measuring ofCYP24 activity comprises measuring CYP24 enzymatic activity in tissues,plasma, or cells.
 35. The method according to claim 1, wherein thetissues or cells are selected from the group consisting of kidneytissue, liver tissue, parathyroid gland tissue, peripheral bloodmononuclear cells, and buccal cells.
 36. The method according to claim1, wherein said abnormally elevated CYP24 expression and/or activity isat least 2-fold increased over normal CYP24 expression and/or activity.37. (canceled)
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